To The Editor:
The review "Low-dose aspirin prevented deep venous thrombosis
and pulmonary embolism after surgery for hip fracture" in
Evidence-Based Orthopaedics (82-A: 1807, Dec. 2000), stated in the
Conclusions section that "In patients having surgery for
hip fracture, low-dose aspirin compared with placebo reduced deep
venous thrombosis and pulmonary embolism, including fatal events.
In patients having elective hip or knee arthroplasty, no reduction was
found."
Despite this conclusion, the opening paragraph of the Commentary
by Dr. Robert B. Bourne states: "This study . . . provides
sound evidence for routinely considering postoperative low-dose aspirin
therapy as a prophylaxis against both PE and DVT
for patients who have had operative treatment for hip fracture, total hip
arthroplasty, or total knee replacement."
This statement seems to be completely at odds with the author’s
conclusion that, although low-dose aspirin is beneficial in hip-fracture
patients, it had no effect in patients treated with elective hip
and knee arthroplasty. I would be most grateful indeed if Dr. Bourne could
resolve my confusion on this point. Does the answer perhaps
hinge on the significance or insignificance of the p value of 0.41?
Even the title of the paper does not include a reference to hip
or knee arthroplasty.
R.B. Bourne replies:
I would like to thank Mr. Grace for his interest in this important
paper by the Pulmonary Embolism Prevention (PEP) Trial Collaborative
Group. I agree with Mr. Grace that the main focus of this paper
was on the prevention of deep venous thrombosis and pulmonary embolism
after surgery for hip fracture. Indeed, 12,356 patients were involved in
the hip-fracture group; 2648, in the hip-arthroplasty group; and
1440, in the knee-arthroplasty group. The authors did conclude that
low-dose aspirin compared with placebo reduced deep venous thrombosis
and pulmonary embolism, including fatal events in hip-fracture patients.
Although the authors could not detect a significant reduction in
deep venous thrombosis or pulmonary embolism in the elective
arthroplasty group, this might be explained by the lower number
of patients enrolled in the arthroplasty group and the fact that the overall
rates of both deep venous thrombosis and pulmonary embolism were
lower in this patient population than they were in the hip-fracture group.
Mr. Grace makes a good point, and I would suggest that the results
of this study—namely, that low-dose aspirin reduced the
risk of deep venous thrombosis and pulmonary embolism—apply only
to the hip-fracture group.